Power Number Calculation For Anchor Agitator

Power Number Equation:

\[ N_p = \frac{P}{\rho \times N^3 \times D^5} \]

Power (P):

Density (ρ):

kg/m³

Speed (N):

rev/s

Diameter (D):

Power Number (N_p):

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1. What is Power Number?

The Power Number (N_p) is a dimensionless number used in mixing engineering to characterize the power consumption of agitators and impellers. It relates the power required for agitation to the fluid properties and agitator geometry.

2. How Does the Calculator Work?

The calculator uses the Power Number equation:

\[ N_p = \frac{P}{\rho \times N^3 \times D^5} \]

Where:

\( N_p \) — Power number (dimensionless)
\( P \) — Power consumption (W)
\( \rho \) — Fluid density (kg/m³)
\( N \) — Agitator speed (rev/s)
\( D \) — Agitator diameter (m)

Explanation: The equation calculates the dimensionless power number by relating the actual power consumption to the theoretical power based on fluid density, rotational speed, and agitator diameter.

3. Importance of Power Number Calculation

Details: Power number is crucial for agitator design, scale-up calculations, and energy optimization in mixing processes. It helps determine the power requirements for different agitator types and operating conditions.

4. Using the Calculator

Tips: Enter power in watts, density in kg/m³, speed in revolutions per second, and diameter in meters. All values must be positive and non-zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for anchor agitator power numbers?
A: Anchor agitators typically have power numbers ranging from 0.2 to 1.5, depending on the specific geometry and Reynolds number.

Q2: How does power number vary with Reynolds number?
A: At low Reynolds numbers (laminar flow), power number is inversely proportional to Reynolds number. At high Reynolds numbers (turbulent flow), power number becomes constant.

Q3: Why is power number important for scale-up?
A: Power number remains constant during geometric scale-up, making it a key parameter for predicting power requirements in larger vessels.

Q4: What factors affect power number?
A: Power number is influenced by agitator type, geometry, baffle configuration, vessel geometry, and fluid properties.

Q5: How accurate is the power number calculation?
A: The calculation provides theoretical values. Actual power numbers may vary due to mechanical losses, non-Newtonian fluid behavior, and specific geometric factors.